<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>向同一个元素添加多个事件且不会覆盖已存在的事件</title>
</head>

<body>
    <p>该实例使用 addEventListener() 方法向同个按钮中添加两个点击事件。</p>
    <button id="myBtn">点我</button>
    <script>
        var x = document.getElementById("myBtn");
        x.addEventListener("click", myFunction);
        x.addEventListener("click", someOtherFunction);
        function myFunction() {
            alert("Hello World!");
        }
        function someOtherFunction() {
            alert("函数被执行！");
        }
    </script>
</body>

</html>